Phonograph motor control



Jan. 31, 1939. wELcH 2,145,743

PHONOGRAPH MOTOR CONTROL Filed Sept. 4, 1937 Inventor AIPr-ed F. WelchHi ttorne Patented Jan. 31, 1939 PATENT OFFICE 2,145.74: rnonoeaarnMoron. con'raor.

sures F. weieh, rm wane, lnd., unmito General Electric Company, acorporation of New York Application September 4, 1981. Serial No.182,500

l'iClaims.

My invention relates to the control of electrically driven phonographsand its object is to provide for control of the motor by the ordinarymovements of the tone arm.

In connection with electrically driven phonographs I have found that itis desirable to apply a higher voltage to the motor at the time ofstarting than when playing the record. Where automatic record changingmechanisms are used it is also desirable to apply a higher voltage tothe motor during the record changing operation. than when playing arecord. The starting and record changing operations require a higheravailable motor torque than is necessary or desirable during the playingof the record, bec'ausegenerally speaking, if a phonograph motor of theusual alternating current synchronous type is energized to obtainmaximum torque output its operation is usually accompanied by an audibleelectromaggo netic hum -whichis undesirable during playing of therecord. According to my invention I provide a driving motor ofsuflicient torque capacity to start the phonograph'into operationpromptly and to perform automatic record changing operations andenergize the motor for high-torque output during such operations. recordplaying period I materialy reduce the voltage applied to the,motor to apoint where its torque is only amply suflicient for this operation andthus obtain unusually quiet operation.- This control ofthe motor isaccomplished by the movement of the tone arm of the phonograph so thatthe necessary switching operations are performed.

understanding of my invention reference is made.

'45 in the following description to the accompanying drawing whichillustrates in Fig. 1 a partial plan view of a phonograph record with atone arm of a phonograph in playing position; P18. 2 .ilhistrates a sideview of electrically driven phonograph apparatus with the tone arm andthe motor control mechanism partially in. section and. with the tone,arm in playing position and the motor energized at reduced voltage; Fig.3 shows the motor;switching.device when the motor is de- I as energized;Fig. 4 shows themotor'switching de- During the vice when the motor isfully energized; Fig. 6 is an enlarged sectional view of a portion ofthe control mechanism shown in Fig. 2; Fig. 5 is a plan view of aratchet mechanism shown in section in Fig. 6 which is used to open themotor circuit when a record has been played, the parts being shown inthe position they will assume when the tone arm is approaching thecenter of the record, and Fig. 7' is another plan view of this ratchetmechanism with its parts in the position they will assume when the tonearm-is swung to one side of the record.

Figs. 1 and 2 show parts of an electrically driven phonograph to whichmy invention is applied. The-record disc is indicated at ill on the turntable II, pivoted at the axis i2 and driven by a self-starting electricmotor II! which is located beneath the top wall ll of the phonographcabinet. The tone arm of the phonograph is shown-at IS. The tone arm ispivoted on a horizontal axis It to a support H in order that the tonearm may be raised and lowered, and the support I1 is secured toa-vertical shaft l8 which is pivoted in a bushing bearing i9 secured inthe top wall of the cabinet. Thus the tone arm'may pivot with shaft itto swing over the record in a horizontal plane and may be raised andlowered by movement about pivot i6, and thus has the usual freedom ofmovement. In Fig. 2 the center .line of the tone arm is marked Run andthis a is the horizontal position of elevation which the tone armassumes when its needle 20 is resting on the record it in playingposition. When the tone arm is lifted from the record its center linewill fall along the line marked "Start". in Fig. 2 u and when the tonearm is swung to one side of the turn table and is lowered to a positionof rest on a rubber button I the center line thereof will fall along theline marked "Oil". The arrangement as thus far described is a usualarrangement.

The vertical shaft ll of the tone arm support is made hollow and withinthis hollow shaft is a switch operating rod 21. The upper end of thisrod has an elongated eye 22 therein through which passes a horizontalpin 23 secured to the tone arm ll. 'lhe pin 23 passes through thevertical axis of rotation of the tone arm and thus freely passes throughthe eye 22 in any rotative pomtion of the tone arm. The lower end-of therod 2i carries an insulated switch operating button 24 which ispreferably screwed on the rod 2| with a tight flt'so that it may beraised and lowered slightly with respect to rod 2| for adjustmentpurposes. The button 24 normally rests on a resilient switch contactmember 25.

The contact member 25 has sufficient resilient strength within its rangeof movement to raise rod 21 unless this is prevented as by reason of thelower limit of the eye opening 22 coming against pin 23. A

Switch contact member 25 cooperates with two additional contact members25 and 21 and these contact members comprise the control switch for themotor IS. The contact members are supported near one end in aninsulating support 28 secured to the under side of the cabinet cover H.The upper contact member 21 is connected directly to one motor terminal29. The central contact member 26 is connected to motor terminal 29through a suitable current reducing resistance 30. The lower contactmember 25 is connected to one side of a supplysource 3| and the otherside of this source is connected to the other terminal of the motor. Thefree ends of the contact arms are provided with cooperating contacts asshown, and the selective opening and closing of these contacts iscontrolled by the vertical position of the tone acting arm through rod2|, button 24 and the lower resilient contact arms 25 and 26.

When the tone arm is raised to the position indicated "start in Fig. 2the contacts of arms -25, 26 and 21 are closed on each other as shown inFig. 4. This connects the motor l3 directly to the source of supply 3|.This places full voltage on the motor and it starts quickly and operatesat full power capacity so long as this switching condition exists.

When the tone arm is lowered to playing position with its needle 20 onthe record disc Ill, position run Fig. 2, contact member 25 is partiallydepressed and this permits resilient contact member 26 to move downwardsufflciently to open its upper contact with contact member 21 as shownin Fig. 2. This inserts resistance 30 in the motor circuit to lower themotor voltage and allows it to run with minimum'magnetic hum. during thetime the record is being played.

When the tone arm is lowered to the position off, Fig. 2, and rests onbutton 9 in, the idle position, which is lower than the playingposition, the contact member 25 is further depressed to open its contactwith member 26 asshown in Fig. 3. It is evident that the tone arm mustbe swung to the side of the turn table in order to be lowered to thisoff position. It is thus seen that using the invention as thus fardescribed the phonograph may be ope a d y child 'any other person merelyby the usual manual movement of the tone arm from a position of rest toany playing position and vice versa, and without consciously performingany switching or manual starting or stopping operation. The switchingmechanism is entirely within the cabinet, which is desirable forprotection. to such mechanism and from the point of view of avoiding'electric'shocks, particularly to children.

Applying a higher voltage to the motor at start than when playing therecord is desirable for several reasons. The reduction in noise duringplaying of the record has been mentioned and is important. Quickstarting is desirable because by the time the operator lifts the tonearm from button 9 and rests it on the record with the needle in theouter groove in the normal manner, the record is up to proper speed andthe dreary sound which is sometimes heard when a phonograph record isplayed on a rising speed is not experienced. The invention makes itpossible to obtain satisfactory operation with some saving inelectricity as compared to that which would be used with a constantvoltage phonograph motor drive system. Some reduction in motor size ispermissible since it will be evident that the torque required of themotor during the actual playing period is small as compared to thatrequired for quick starting. With my invention it is permissible to usea relatively small motor and momentarily overenergize it to obtain highpower for starting since the starting period is very short and startingoperations are time spaced 'sumciently that heating of the motor due tosuch momentary and relatively infrequent starting is not a troublesomefactor. The voltage control of the motor as hereinbefore described issuitable for and desirable with automatic record changing phonographs. Ihave not shown such automatic changing features and this is unnecessaryto support the truth of this statement, since it will be observed thatwhether a record is changedcapacity is thus available to start the motoror to perform any other extra duty that should be or is performed whenthe tone arm is in a raised position.

In the ordinary phonograph not equipped with record changing apparatusit is desirable that when the apparatus has finished playing a record itwill shut itself down automatically and a mechanism for performing thisoperation will now be described. Phonograph records may be made and manyof them as now made have an inner eccentric groove 32 (see Fig. 1) intowhich the needle 20 of the phonograph arm is guided when the playing ofthe record is completed. If the motor continues to run, the eccentricgroove gives the tone arm a back and forth rotary motion about. itsvertical pivot point. I make use of the horizontal movement of the tonearm over the final range of its movement to' this record ending positionwhere the needle is in groove 32 and, if necessary, the back and forthmotion of the tone arm as the needle rides in the eccentric groove 32for operating a ratchet device best shown in Figs. 5 and 7 for movingswitch rod 2| downward to open the circuit of the driving motor l3 atcontacts 25 and 26 notwithstanding the fact that the tone arm remains atplaying elevation.

Secured in fixed relation to the bottom of hol- 36. The ratchet wheel isfree to turn and has a bearing on hollow'shaft 19. The ratchet wheel isnormally biased to the rotary position shown in Fig. '7 by a spring 31secured between a staf tionary post 38 and an off-center pin 39protruding from the upper side of such ratchet wheel.

In the rotary position of ratchet wheel 35 shown in Fig. 7 it ispreferably prevented from-J further rotation in a counter-clockwisedirection by a stop pin 49 against which a shoulder ll of the ratchetwheel is urged by spring 31.

A. check pawl 42 is provided. This pawl is pivotedon a post 43 and thepawl is urged against ratchet wheel 35 by a spring 44. The check pawl 42carries an elongated finger 45 which serves to remove both the advancingpawl 34 and the check pawl 42 from the ratchet wheel when the tone armis swung counterclockwise to a record beginning position where itsneedle end is opposite the outer record groove or beyond to one side ofthe record such as the position designated by line I50, Fig. 7. Thisresult is accomplished by reason of the rear end of pawl 34 striking theinner surface of finger 45. Both pawls are turned counter-clockwise ontheir pivot points and their pawl ends are retracted from the ratchetwheel. As soon, however, as the tone v arm approaches the end of playingrange and reaches some such position as lib, Fig. 5, which is about theposition of the tone arm shown in Fig. 1, finger 45 releases pawl 34 andboth pawls return to ratcheting position against. ratchet wheel 35. Theposts 38, 40 and 43 may extend downward from the top of the cabinet asshown for post-43, Fig. 2. It will now be evident that when the tone armreaches some such playing position as shown in Fig. l, ratchet wheel 35will be caught by pawl 34 and will then turn in a clockwise directionmoving shoulder 4| away from stop pin 4. until the playing of the recordis completed and the tone arm moves to the record ending groove 32 andthen, if necessary, as the tone arm takes up the wobbling or'back andforth rotary motion, pawl 42 will hold the ratchet wheel from returningas pawl 34 backs up and advances and ratchets the wheel 35 further in aclockwise direction against the restraining action of spring 21. Theteeth of the ratchet wheel should be spaced not greater than the throwofratchet pawl 34 when the tone arm takes up the wobbling motion.

Projecting from the under side of ratchet wheel 35'is abutton 48 whichacts with a cam sector 41 secured to switch actuating post 2| to movethis post downward as ratchet wheel is advanced in a clockwisedirection. Downward movement of post 2| is permitted independently ofthe tone arm by reason of the lost motion connection consisting of theelongated eye 22 in the top of post 2| where it is hooked to the tonearm by the pin 23. The post 2| and cam sector 41 are prevented fromrotating with respect to the tone arm by pin 23.

The parts are so adjusted that as the needle moves the tone arm from thefinal music playing groove to the groove 32 or shortly'after the tonearm needle reaches the eccentric groove 22 and gives the tone arm a fewback and forth ratcheting movements upon the completion of the playingof a record, cam button 46 will have advanced far enough on the risingsurface of cam sector" to move post 2| down sufilciently to open switch25, 26 as shown in Fig. 3. Hence, the motor is stopped automatically asor shortly after a record is'completed if the apparatus is leftunattended.. This performs the same switching result as is accomplishedby lowering the tonearm and of course it is unnecessary to allow theapparatus tocut off automatically if an attendant is present and raisesthe tone arm and returns it to "of!" position before the automaticcut-oif has an opportunity to complete its action. .Whether theautomatic cut-off device has completed its action or otherwise, suchautomatic The cam sector 41 isin the shape ofan L and is resilient sothat the tone arm may be raised and with it post 2| even though the cambutton 48 is on the high part ofcam sector 41 and is urging the post 2|downward. The fact that cam sector 41 has some resiliency does notprevent it from moving post 2| downward against the tension oi switchcontact finger 25 in an automatic shut-off operation because at thistime the only force opposing such downward movement is the relativelylight upward tension of spring contact finger 25.

When the tone arm is raised from near the center of the record and whileraised during its movement to "o position, it will be evident that themotor will be momentarily fully energized.

This does no harm and in fact if the same record is to be replayed it isdesirable, as then the record will be up to speed as the tone arm islowered into playing position. It is contemplated that a synchronousdriving motor will be used so that its full operating speed will becorrect regardless of the voltage applied thereto. The entire starting,stopping and torque control mechanism is inclosed and protected. Thereare no switches or other starting or stopping gadgets exposed.

In accordance with the provisions of the patent statutes, I havedescribed the principle of operation of my invention together with theapparatus which I now consider to represent the best embodiment thereofbut I desire to have it understood that the apparatus shown is onlyillustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent in the UnitedStates is:

' 1. In a phonograph, a turn table, an electric motor for driving saidturn table, a tone arm pivoted for movement about a horizontal axis suchthat the tone arm may be raised above and lowered to a playingpositioman energizing circuit for said motor, voltage changing means forsaid motor associated with said circuit, and means associated with thetone arm and operated by such raising and lowering movement of said tonearm for controlling said voltage changing means to respectively increaseand decrease the voltage applied to said motor.

2. In a phonograph, a turn table, an electric motor for driving saidturn table, a tone arm pivoted so as to be raised above and loweredbelow a playing position with respect to said turn table, an energizingcircuit for said motor including circuit opening means and voltagechanging means, and means operated by saidtone arm for opening andclosing said circuit as the tone arm is lowered below and raised toplaying position respectively, and for increasing and decreasing thevoltage applied to said motor as the tone arm is raised above andlowered to its playing position respectively.

3. In a phonograph, a turn table, an electric motor for driving saidturn table, a tone arm pivoted so as to be raised above and loweredbelow a playing position with respect'to said turn table,

an energizing circuit for said motor, a voltage reducing resistance,switching means for opening and closing said circuit and cutting saidresistance in and out of said circuit, and means operated by the raisingand lowering movements of said tone arm for operating said switchingmeans such that when the tone arm is below playing position the motorcircuit is open, when the tone arm is in playing position the circuit isclosed through said resistance and when the tone arm is raised aboveplaying position the circuit is closed independently of said resistance.

4. In a phonograph, a turn table, an electric driving motor for saidphonograph, a tone arm pivoted so as to be raised above and lowered to aplaying position with respect to said turn table, a hollow verticalshaft to one side of said turn table pivoting said tone arm about avertical axis, an energizing circuit for said motor, control meanstherefor, and means secured to said tone arm and passing through saidhollow shaft for operating said circuit control means in response to theraising and lowering movement of said tone arm,

5. In a phonograph, a turn table, an electric driving motor therefor, atone arm pivoted for movement about a vertical axis to one side of saidturn table so as to be swung to and from a playing position over saidturn table, and pivoted about a horizontal axis so as to be raised aboveand lowered to a playingposition with respect to said turn table, anenergizing circuit for said motor, circuit control means therein, and anoperating member for said control means connected to said tone arm so asto be operated by the raising and lowering movements thereof when thetone arm is in any rotative position about its vertical axis ofrotation.

6. In a phonograph, a record supporting turn table, a tone arm pivotedto swing in a horizontal plane over said turn table between recordbeginning and record ending positions and also pivoted for verticalmovement above and below a record playing position with respect to saidturn table, an electric motor. for driving said turn table, a switch forsaid motor, means operated by the raising of said tone arm to playingposition for closing said switch and means operated by the horizontalmovement of said tone arm to record endingposition for opening saidswitch while the tone arm remains in a vertical playing position.

7. In a phonograph, a record supporting turn table, a tone arm pivotedto swing over said turn table in a horizontal plane, inclusive of arecord playing range, from an outer record beginning position to aninner record ending position, and pivoted for vertical movement aboveand below record playing positions, and having a position of restoutside the record playing range and below record playing position, anelectric motor for driving said turn table, a switch for said motor,means operated by the raising of said tone arm from said position ofrest to playing position for closing said switch to start the motor andmeans operated by inward horizontal movement of said tone arm foropening said switch after moving through the record playing range.

8. A phonograph, comprisinga recordi supporting turn table, a tone armpivoted to swing over said turn table in a horizontal plane from anouter position to one'side of said turn table, inwardly through a recordbeginning position and through a record playing range to an inner recordending position, and also pivoted for vertical movement from belowrecord playing position to above record playing position, said .tone armhaving a position of rest to one side of the turn table and belowvertical playing position, an electric motor for driving said turntable, a switch for starting and stopping said motor, and means operatedby the movements of said tone arm for closing and opening'said switch,said means being so correlated with the switch and tone arm that theswitch is open when the tone arm is in said posifor starting andstopping said motor, a tone arm pivoted for horizontal movement oversaid turn tableirom an outer record beginning position to an innerrecord ending position, ratchet means operated by the inward movement ofsaid tone arm as it approaches record ending position during a recordplaying operation for opening said switch, said ratcheting means beingrendered ineffective by outward movement'of the tonearm from recordending to record beginning position whereby the switch is permitted toclose.

10. In a phonograph, a record supporting turn table, a groovedphonograph record thereon, a tone arm pivoted for movement in ahorizontal plane, a needle on said tone arm adapted to rest upon therecord to guide the tone arm over the record in a record playingoperation, an elec tric motor for driving said record, a switch for saidmotor and means responsive to the horizontal movement of said tone armin a record playing direction for opening said switch and responsive tomovement in the, opposite direction for closing said switch.

\ 11. In a phonograph, an electric driving motor therefor, a switch forsaid motor, a pivoted tone arm for said phonograph, means responsive tothe operation of the phonograph for swinging said arm through a recordplaying range from a record beginning position to a record endingposition, said tone arm being manually returnable from the record endingposition to the record beginning position, and means responsive to suchmovements of said tone arm for opening and closing said switch such thatthe motor is automatically stopped when a record playing operation iscompleted and is restarted when the tone arm is manually returned torecord beginning position.

12. In a phonograph, a tone arm, a vertical shaft on which said tone armis mounted to swing in a horizontal plane from a record beginningposition, through a record playing range to a record ending position andreturn, a ratchet wheel rotatively supported on such vertical shaft andbiased to an initial rotative position, a ratchet pawl for said ratchetwheel which is rotated about the periphery of the ratchet wheel in adirection to advance said wheel with said tone arm when the latter ismoving towards record ending position, a check pawl for said ratchetwheel, means biasing said pawls against said ratchet wheel, a motor forsaid phonograph, motor control means for starting and stopping saidmotor, means operatedby said ratchet wheel when advanced by said pawlsfor operating the motor control means to stop the motor, means operatedby the return movement of said tone arm to record-beginning position forreleasing said pawls thereby allowing the ratchet wheel to return to itsinitial position, and resilient means for operating the motor controlmeans to start said motor when said ratchet wheel is returned to itsinitial position.

13. A phonograph, an electric motor for driving said phonograph, aswitch for controlling said motor, a tone arm for the phonograph mountedfor rotation back and forth about a vertical axis and pivoted-formovement up and down about a horizontal axis to permit of the usualfreedom of movement of the tone arm in the normal operation of suchphonograph incident to the playing and changing of records and meansresponsive to both of such movements for opening and closing of saidswitch.

14. A phonograph, an electric motor for driving said phonograph, aswitch normally biased to closed position for controlling said motor, atone arm mounted for rotation about a vertical axis between recordbeginning and record ending positions and inclusive of a record playingrange, and'mounted for rotation about a horizontal axis for movementabove and below a record playing elevation, means responsive to thelowering of said tone arm below record playing elevation for openingsaid switch, and means responsive to movement of said tone arm to recordending position for opening said switch.

15. A phonograph including a cabinet, a horizontal record supportingturn table above the top wall of said cabinet, a hollow shaft extendingthrough the top wall of said cabinet to one side of said turn table, avertically movable tone arm secured to said shaft above said wall, anelectric motor for driving said turn table and a control switch for saidmotor beneath said wall, a parthooked to the under side of said tone armand extending downward through said hollow shaft for operating saidswitch in response to the vertical movements of said tone arm,'and meansbeneath said wall operated by rotational movement of said shaft and tonearm also for operating said switch, said two switch operating 16. In aphonograph a turn table, a tone arm,-

a hollow vertical shaft therefor, said tone arm being secured to saidshaft by a horizontal pivot which permits raising and lowering of thetone rarm, an electric motor for driving said turn table,

aswitchforeontrollingsaidmotor,apoctextending between the tone arm andthe vicinity of said switch through said hollow shaft for operating saidswitch in response to vertical movements of said tone arm, a ratchetmechanism operated by the rotary movement of said tone arm and shaft,and cam means between said ratchet mechanism and post whereby saidswitch means may also be operated by rotary movement of said tone arm,there being a lost motion connection between said post and tone armwhereby said post may be moved by the cam means to operate the switchmeans-without vertical movement of said tone arm.

17. In a phonograph, a record-supporting turn table, a tone arm pivotedfor rotation in a horizontal plane over said turn table from an outerposition to one side of said turn table, inwardly through arecord-beginning position adjacent the periphery of the turn table,through a record playing range, to a record ending position near thecenter of the turn table, said tone am also being pivoted for movementin a vertical plane to permit its being moved above and belowrecordplaying elevation, said tone arm having a position of rest to oneside of said turn table and below record playing elevation, an electricmotor for driving said turn table, an energizing circuit for said motor,circuit controlling means associated with said circuit forenergizing-and decnergizing the motor and for varying the voltageapplied thereto, and means controlled by the horizontal and verticalmovements of said'tone arm for operating said circuit controlling means,to deenergize the motor when the tone arm is moved to its position ofrest, to energize the motor at a given voltage when the tone arm is.

raised above playing elevation, to energize the motor at a lower voltagewhen the tone arm is lowered.to playing elevation at record beginningpofltion, to maintain the motor energized at such lower voltage when thetone arm is moving inwardly over the record playing range when at recordP y g elevation and to deenergize the motor when the tone arm reachesrecord ending position while at record P1881118 elevation.

m r. WEI-CH."

